In a communication system, in transmission of physical data channels of a User Equipment (UE), the UE needs to be informed through scheduling assignment instructions of the system. A Physical Downlink Control Channel (PDCCH) bears the scheduling assignment instructions, where the scheduling assignment instructions are, for example, a downlink scheduling grant (DL_grant) corresponding to a Physical Downlink Shared Channel (PDSCH) and an uplink scheduling grant (UL_grant) corresponding to a Physical Uplink Share Channel (PUSCH).
In a single-carrier Frequency Division Duplex (FDD) system, data can only be transmitted between the UE and a network side on a pair of uplink and downlink carriers, and the PDCCH may bear the DL_grant and the UL_grant, which are used for instructing the scheduling of downlink and uplink physical data channel resources corresponding to the UE on the carrier pair. However, after the multi-carrier technology is introduced, the data can be transmitted between the UE and the network side on a plurality of carriers or carrier pairs at the same time, and scheduling signaling of a data channel on each carrier is independently coded, so one PDCCH is required to bear the resource scheduling signaling on each carrier.
In a multi-carrier system, for one UE, the PDCCH of the UE is transmitted on each component carrier, for scheduling the transmission of the PDSCH on the component carrier or the PUSCH corresponding to the component carrier. Alternatively, for one UE, all the PDCCHs of the UE is transmitted on one component carrier, that is, the control channel may instruct the transmission of the service channels on the downlink component carrier of the control channel and the corresponding uplink component carrier, and may also instruct the data transmission on different downlink component carriers or on component carriers that are not correspondingly uplink paired.
When all the PDCCHs of one UE are transmitted on one component carrier, as a size of a search space is limited, the impact probability is high, and the PDCCH of the UE may fail to be transmitted, thereby causing that a part of data of the UE fails to be transmitted.